For the overall project the objective is to determine the stereochemical courses of enzymatic substitution at phosphorus, with special reference to the question of retention or inversion of configuration at phosphorus in phosphotransferase and nucleotidyltransferase reactions. In the current year our efforts have concentrated on the synthesis of chiral phosphates and stereochemical studies of nucleoside phosphotransferase, nucleoside diphosphate kinase, and DNA polymerase.